A passive optical network (PON) technology is a point-to-multipoint (P2MP) optical access technology, and a PON system includes an optical line termination (OLT), an optical splitter (OS)/extender box (EB), optical network units (ONUs)/optical network terminals (ONTs), and optical fibers for connecting devices.
As an office end device, the OLT is connected to the OS/EB through a trunk optical fiber. The OS/EB is connected to each ONU through an individual branch optical fiber. The trunk optical fiber exists between the OS/EB and the OLT, and several branch optical fibers exist between the OS/EB and the ONUs. In a downlink direction (OLT→ONU), the OS/EB implements a light splitting function to send a downlink optical signal of the OLT to all the ONUs through the branch optical fibers. In an uplink direction (ONU→OLT), the OS/EB implements an optical signal aggregation function to aggregate optical signals sent by all the ONUs and send the aggregated optical signals to the OLT through the trunk optical fiber.
Currently, in order to eliminate a fault of the trunk optical fiber between the OS/EB and the OLT or an OLT fault, a 1+1 protection architecture as shown in FIG. 1 is generally adopted. The architecture adopts two sets of trunk optical fibers and OLTs, where one set of trunk optical fiber and OLT is active and the other set of trunk optical fiber and OLT is backup, to form 1+1 protection for the trunk optical fibers and the OLT. When the trunk optical fiber or the OLT is faulty, the backup OLT takes over the ONUs under the original active OLT. An aggregation node (AggN) or aggregation switch (AGS) is connected to the active OLT and the backup OLT through an active port and a backup port respectively. Alternatively, an active aggregation node and a backup aggregation node are connected to the active OLT and the backup OLT respectively. Similarly, an N:1 PON protection architecture may also be adopted, which will be discussed with reference to FIG. 3.
It is observed that, conventionally, when the active OLT or the trunk optical fiber between the active OLT and the OS (or EB) is faulty, a corresponding PON port of the active OLT is switched to the backup OLT, so the aggregation node cannot be notified that joint switching is required, and a link between the aggregation node and the active OLT cannot be jointly switched to a link between the aggregation node and the backup OLT, causing that the communication link cannot be restored to normal.